Refrigeration systems or “cold cases” are a necessary part of modem food retailing. These systems function to both keep fresh food cold or else to freeze food, depending on the temperature at which the system is set. Depending on the demand for certain types of foods, food retailing establishments regularly change the temperature settings of their systems to accommodate these changing demands. Typically, supermarkets contain, on average, about 75 refrigerated cases per store. A system for monitoring such a large number of cases is essential in order to maintain proper temperature, and therefore optimal food quality, for as long as possible. Additionally, refrigeration monitoring systems are necessary to reduce food spoilage loss resulting from malfunctioning refrigeration cases.
Basic thermometers installed in each refrigeration case represent the most rudimentary monitoring solution employed in the food industry. These thermometers can be of the common dial or digital type. However, typically thermometers must be mounted inside of the refrigeration case for proper functioning, which makes them difficult to find, and more often than not they become hidden behind food merchandise. Also, thermometers require trained personnel to monitor them constantly and to be able to interpret the temperature readings. Additionally, power outages or technical malfunctions may cause a cold case to enter a defrost mode. Thermometers are often insufficient tools for alerting store personnel to the impact upon food merchandise caused by these defrost cycles. Also, thermometers often cease to function properly; a fact that often goes unnoticed when thermometers are hidden behind food merchandise Health inspections commonly result in citations issued to replace damaged or broken thermometers, which result in follow up inspections that are costly for the retailer.
Due to the deficiencies inherent with thermometers, a majority of large food retailers have employed thermistors to sense temperature, which are remotely monitored by a computer, that is often located hundreds of feet away in a store's mechanical room. An example of such a system is seen in U.S. Pat. No. 6,378,315 issued to Gelber et al. The thermistors communicate to the computer via analog means, wherein the analog signal is transmitted by individual “point to point” single pair wire runs from the remote computer to each thermistor located in the cases. However, such systems are expensive to install due to the high labor costs involved in installing enough temperature sensors, as well as installing the large amount of wire required to accommodate the sensors. Furthermore, analog technology is susceptible to interference from fluorescent lighting which increases the greater the distance which the analog signal needs to travel. In an indoor retail establishment fluorescent lighting creates substantial interference with analog signals being transmitted over long wire lengths. In some large warehouse stores, the distance between the sensors and a practical location for a monitoring computer can be up to 1500 feet, in which case an analog system experiences many sensor faults and inaccuracies.
Current wireless offerings, such as that seen in the '315 Gelber patent have not been popular because of the cost and lack of reliability associated with these systems. These systems require that the temperature sensor located in a single case to be a standalone wireless device that communicates to the remote controller through a single transmitter to a repeater (recommended every 150′) and finally to a master receiver which communicates this information to the controller. These sensor transmitters are battery powered and must have a line of site to the receiver or repeater in order to maintain communication. In a retail environment it is impossible to ensure that all 70+ transmitter sensors have a proper line of site upon installation. Also ongoing merchandising changes involving placing displays, hanging plants, or moving merchandise often places objects in the path of the line of site transmission, thereby blocking communication between the cold case sensors and the remote controller.
Furthermore, large refrigeration cases can be 12 feet in length, lending to the existence of separate cold zones having different temperatures. The same food merchandise placed in one optimal cold zone may experience deterioration in an adjacent cold zone having a temperature that is less than optimal. With health department standards becoming stricter, it is believed that monitoring separate cold zones present in the same refrigeration case will increasingly become an issue.
Therefore, a need exists for a refrigeration monitoring system which is capable of re-routing wirelessly transmitted signals around objects until a clear line of site can be achieved. A need also exists for a refrigeration monitoring system which allows the reliable monitoring of cold cases by untrained personnel and which is not susceptible to electrical interference problems inherent with analog systems. Furthermore, a system having the ability to monitor multiple cold zones located in the same refrigeration case would be desirable. In addition to these improvements, it would also be desirable to have a system which be installed with a minimal amount of wiring, thereby reducing system cost.
The foregoing reflects the state of the art of which the inventor is aware, and is tendered with a view toward discharging the inventor's acknowledged duty of candor, which may be pertinent to the patentability of the present invention. It is respectfully stipulated, however, that the foregoing discussion does not teach or render obvious, singly or when considered in combination, the inventor's claimed invention.